The present invention relates to a safety device for a motor vehicle gearbox of the type comprising a first shaft carrying a first series of gears connected for rotation with it, and a second shaft carrying a second series of gears which are freely rotatably mounted on the said second shaft and which are in constant mesh with respective gears of the first shaft, and a plurality of coupling devices for connecting respective gears of the said second series for rotation with the said second shaft.
The invention relates in particular to a safety device for a motor vehicle gearbox control, of the type comprising a plurality of selector rods slidable parallel to one another in the casing of the gearbox and each carrying at least one fork member for controlling a respective coupling device, each selector rod being displaceable between a neutral position and at least one operative position, and locking means for locking, with respect to the gearbox casing, all the selector rods with the exception of that which is selected at the time, the said locking means including a series of locking dowels slidable in respective seats in the gearbox casing and having active ends adapted to cooperate with respective reference notches provided on the selector rods when these are in their neutral positions so that, when a selector rod is moved away from its neutral position, the other selector rods are retained in their neutral positions by the engagement of the said locking dowels in the respective reference notches.
A control device of the type indicated above is, for example, described and illustrated in European Patent EP-B-0170630. In the conventional arrangement of this type, the axes of the selector rods are disposed in the same plane. This involves the necessity of providing the various selector rods with fork members of different shapes and dimensions, the distance from the axis of each selector rod to the axis of the shaft with which the coupling devices are associated being different from that of the other selector rods.